Flight Termination

Comet Air & Ground

Comet is a radio-linked remote-stop or flight termination system with digital, pyrotechnic, CAN-FD, serial, and Ethernet outputs. Designed to ensure no single failure shall cause termination, Comet comes with dual redundant processing and redundant termination circuits. Both Comet Air and Ground come with dual Ethernet or dual CAN-FD telemetry links which can be used as a soft source of termination information and source of system diagnostics.

In the standard configuration, a single Air unit supports up to two Ground units in line-of-sight operation. Mesh and repeater options allow beyond-line-of-sight operation and range extension. Protocol extensions allow up to eight Ground units.

A socketed radio solution allows Comet to support many popular bands from 400 MHz to 2.4 GHz and transmit power of up to 4 Watts. Licensed and unlicensed variants are available depending on the country of operation.

Interface Control Document
Overview

Comet Air has two termination outputs which can be independently configured for positive-logic digital or pyrotechnic ignition function. Termination voting can happen internally or externally, and the output can optionally be latched and held-up for a short period of time.

Comet Ground comes standard with an 8-hour battery, neck lanyard, daylight visible LEDs and a loud buzzer; allowing range safety officers to operate from any location. A rubber duck antenna and neck lanyard is provided as standard, but the unit is also capable of fix location operation via the EN-4165 connector, which can also provide telemetry.

Termination Chain

Radio

Microhard Pico Series
Time shared between processors, independent signing keys

CPU

Dual Independent STMicro STM32H7
400MHz ARM Cortex M-7 with Double Precision Floating Point Unit
2MB Internal Flash
1MB Internal RAM

Voting

Each termination lane has independent Arm, Terminate, and Safe logic assemblies. This structure allows each lane to vote with logical AND, OR, or be lane independent.

Single lane voting topology
Communication

External to System

Option 1
Dual 10/100 Ethernet
Single RS-232

Option 2
Single 10/100 Ethernet
Dual CAN-FD
Single RS-232

Between Lanes

Optional UART connection between processor lanes for more complex voting and status sharing algorithms.

RF Performance

Band TX Power (W) Sensitivity (dBm) Range (km)
400 MHz 2 -114 110
840 MHz 2 -114 50
866 MHz 1 -114 35
869 MHz 0.5 -112 20
900 MHz 1 -110 20
2.4 GHz 1 -112 10

Range is an estimate and assumes clear line of sight, uniform radiation patterns, 1km receiver altitude, 20dB link margin, and default link rates, bandwidths, and error correction. Real world performance depends on many additional factors.

Physical

Weight

Air: 375g

Dimensions

Air Unit
Length: 5.9 inches
Width: 4.4 inches
Height: 1.6 inches
Modified Hammond 1590BB

Ground Unit
Modified Hammond 1590KK

Mounting

Air Unit
4x countersunk chamfered slots
1x counter sunk electrical bonding stud

Ground Unit
None

Custom base plates for mounting and electrical bonding are possible.

Power

Input Voltage

Air
18 to 30V (nominal)
DO-160G §16.6 Category B

Ground
25.2V maximum charge voltage

Power Consumption

5W typical, unterminated
Meets DO-160G §16.7.5, Inrush

Redundancy

Comet FTS Air has dual power inputs, internally ORd together with ideal diodes and clamped. This is a common power input feeling a set of shared holdup capacitors and regulators.

Termination power can either be jumped directly to the ORd input rail without clamping and holdup, or after the clamp with holdup.

Enviornmental

Comet FTS was subjected to formal environmental qualification testing. For more information, please contact allocortech.

Temperature

Air:
DO-160G §4.5 Category B2
DO-160G §5 Category B

Ground:
DO-160G §4.5, with minimum temperature of -20°C and maximum of 60°C due to internal battery.
DO-160G §5, with restricted temperature range as above.

Condensing Humidity

DO-160G §10.3.1

Vibration

Air: DO-160G §8 Category R/Fixed-Wing

Operational Shock

Air: DO-160G §7.2 Category A

Altitude

Air: DO-160G §4.6.1 Category B2 (-5k to 25k ft MSL)
Ground: DO-160G §4.6.1 Category B2 (-5k to 8k ft MSL)

Induced Susceptibility

Air: DO-160G §19.3.3 and §19.3.4 Category CW

Drop Resistance

Ground: Operating survival of 7 foot drop onto any corner and any face

Debug

Debugging

JTAG and ST SWI

Programming

Internal JTAG Header, RS-232 ST Bootloader, allocortech bootloader over CAN, RS-232, or Ethernet

allocortech has many supported custom configurations of the Comet FTS AIR that can be created upon request.  The base part numbers are listed here:

  • 100-0050-001 —
    COMET FTS Air ERHHSSLLDD900
  • 100-0050-002
    COMET FTS Air CPHHVVTTDD900
  • 100-0050-003
    COMET FTS Air EPHHSSLLDD900
  • 100-0051-001 —
    COMET FTS Ground